The present invention relates to hydraulic apparatus for driving rods and the like into the ground.
It is well known that it is desirable to provide ground rods along electrical transmission lines and adjacent other poles and elevated towers so as to provide a good ground connection for a ground wire from the structure with which they are associated. Although it is possible to drive such rods into the ground by hand using a mallet or the like, frequently the desired length of the rods will require the workman to stand upon a platform or the like in order to be able to strike the upper end of the rod. As a result, long rods are frequently driven into the ground by use of a pavement breaker or the like operated from an elevated platform or hanging from a boom or a crane.
However, more recently, manually held apparatus has been proposed to drive elongated rods into the ground, and this apparatus may be operated with the operator standing on the ground. In such apparatus, the rod extends through a central passage in the hydraulic driver, and the rod is repositioned as it is being driven into the ground. Exemplary of such devices are those illustrated in Smolyanitski et al U.S. Pat. Nos. 4,205,727 and 4,487,273 and Kostylev et al U.S. Pat. Nos. 4,516,662 and 4,776,407. As will be noted from a review of the structures of these patents, generally it is required that the driver be in intimate contact with the surface of the ground so that the clamping mechanism about the rod will be released during the recoil portion of the drive stroke and thereby repositioned. Moreover, devices of this type generally require serrated jaws or the like to quickly and instantaneously grip the rod during the drive portion of the stroke. Thus, they present the potential for undesirable marring of the galvanized or other protective surface provided upon the rod.
It is an object of the present invention to provide a novel ground rod driver which provides continuous firm gripping of the rod until it is released by an intentional action of the person operating the rod driver.
It is also an object to provide such a ground rod driver which firmly grips the ground rod in the jaws of a chuck assembly so as to preclude relative movement until such time as the chuck jaws are moved outwardly from gripping contact by intentional operation of the clamping mechanism.
Another object is to provide such a ground rod driver which is rugged in construction and long lived in operation.